Gyroscopically controlled gunsight



Oct- 24, 19 0 L. B. c. CUNNINGHAM ETAL 2,527,245

GYROSCOPICALLY CONTROLLED cuusxcm Filed Mqrch 1v, 1944 5 Sheets-Sheet 1VTO is m o v Wi e-pd,

i dmm Attorney Oct. 24, 1950 1.. B. c. CUNNINGHAM ETAL 2,527,245

GYROSCQFICALLY CONTROLLED GUNSIGHT Filed March 17, 1944 Sheets-Sheet 2F/GZ.

66 ,5 1. Wm a 04 67150 70 Gun) 2% 5% WM" y [26L Mat/mm Attorney Oct. 24,1950 B. c. CUNNINGHAM ETAL 2,527,245

GYROSCOPICALLY CONTROLLED cuusmu'r Filed March 1'7, 1944 5 Sheets-Sheet3 F/GB.

/ v YENTO/FS A tlorney Oct. 24, 1950 B. c. CUNNINGHAM ETAL 2,527,245

' GYROSCOPICALLY CONTROLLED GUNSIGHT Filed March 17, 1944 5 Sheets-Sheet4 Attorney Oct. 24, 1 0 L. B. c. CUNNINGHAM Er'AL GYROSCOPICALLYCONTROLLED GUNSIGHT Filed March 17, 1944 5 Sheets-Sheet 5 vE/v TO ITSPatented ct. 24,

UNITED STATES PATENT OFFICE GYROS COPICALLY CONTROLLED GUN SIGHT LeslieBennet Craigie Cunningham, Stanmore, and Howard Ford, Jeffery WaltonBarnes, Ben Sykes, Maurice Hancock, and Bernard Wheeler Robinson,

Farnborough, England; Barclays Application March 17, 1944, Serial No.5.263753% In Great Britain August 22, 1942 8 Claims.

The invention relates to an improved gunsight.

Whenever relative motion takes place between a gun and its target, or,when relative motion takes place between the gun and the surrounding airhaving a component in a direction at right angles to the gun barrel,giving rise to bullet trail, or when the gun barrel is not parallel tothe direction of the earths gravitational field, giving rise to bulletdrop, it is necessary to point the gun in a direction different fromthat of the straight line joining it to the target in order to hit thetarget. When these various conditions exist simultaneously, the requiredangle between the gun barrel and the straight line joining the gun tothe target is the vector sum of the angles necessitated by the saidseparate factors. This resultant angle between the gun barrel (the lineof aim) and the line joining the gun to the target (the sighting line)is termed the deflection angle.

In conventional practice, when using non-automatic gunsights, the gunnerestimates the required deflection angle approximately by the applicationof simple standardised rules and aims accordingly. The exact evaluationof the required deflection angle involves consideration of the followingfactors:

(u) the velocity of the target relative to the gun,

(b) the range of the target,

() the velocity of the air relative to the gun,

(d) the density of the air along'the trajectory of the projectile,

(e) the direction of the earths gravitational field relative to the gun,

(I) the ballistic characteristics of the gun and the projectiles.

It is therefore a matter of considerable complexity. The approximateestimate of the required deflection angle obtained by the application ofsaid standard rules is therefore frequently in considerable error, andis known to be responsible for much ineffective shooting.

The invention has the object of enabling such aiming allowance to bemade automatically by interposing a variable deflection angle betweenthe sighting line and the line of aim by automatic adjustment of thegunsight, which may be termed a predictor gunsight, sinceit enables therequired deflection angle to be automatically computed and maintained.

In accordance with the present invention, an automatic predictor.gunsight comprises means for indicatin a sighting line, a mechanism forcontinuously evaluatingl'the required deflection angle to a desireddegree of precision while said sighting line is pointed continuouslytowards the target, and means for interposing said deflection anglebetween the sighting line and the line of aim by causing said indicatedsighting line to move relative to the body of the sight.

In a convenient form, the gunsight may com pris a constrained gyroscopecoupled mechanically or optically with an optical sight, said gyroscopeand optical sight being associated with, and mounted in close proximitywith a gun or group of guns in such a manner that the equilibriumdirection of the spin axis of the gyroscope, the indicated sightingline, and the axis of the gun barrel or controidal axis of the group ofgun barrels are parallel when the required deflection angle is zero.When the mounting of said gyroscope is rotated to follow a relativelymoving target, the spin axis of said gyroscope will deviate from its norotation equilibrium position relative to said mounting by an amount andin a direction governed jointly by the nature of said rotation and thecharacteristics of said constraint. In this form of gunsight saidconstraint may take the form of a precessing torque whose magnitude isvery nearly proportional to the deviation of the gyroscope spin axisfrom its equilibrium position for no rotation, and whose direction issuch as to cause said axis to move directly towards said equilibriumposition. In consequence, it follows that when the mounting is rotatedwith uniform angular velocity, the spin axis will take up an equilibriumposition which lags behind said no rotation equilibrium position by anamount which is proportional to said uniform angular velocity, and in adirection parallel to the plane of said rotation, or, when said angularvelocity is not uniform, the magnitude and direction of said lag willvary from their equilibrium values appropriate to uniform rotation byamounts proportional to the rate of change of said rotation.

When relative motion takes place between the gun or guns and target, thecomponent of the deflection angle required to allow for this factor isproportional to the product, angular velocity of sighting line requiredto follow target multiplied by time of flight of projectile from gun totarget, and is in the plane of said rotation provided said angularvelocity is uniform, or, is nearly proportional to said product and insaid direction when said angular velocity does not change rapidly. Sinceconditions involving rapid change of angular velocity of sighting lineare rarely encountered in practical gunnery, it follows that the lag ofsaid constrained gyroscope from its no rota-.

3 tion equilibrium position will, in all practical cases, be nearlyproportional to that component of deflection angle required to allow forrelative movement between guns and target so long as the mounting ofsaid gyroscope is moved so as to partake of said relative movement.

When conditions are encountered which introduce into the requireddeflection angle corrections for bullet trail and bullet drop, saidcorrections being termed trail and gravity angles respectively, th norotation equilibrium position of the gyroscope spin axis may bedeflected from its initial position through an angle proportional to thevector sum of trail and gravity angles. Accordingiy, when the gyroscopemounting is rotated to follow a relatively moving target in thesecircumstances, the total deviation of the gyroscope spin axis from itsinitial no rotation equilibrium position will be proportional to thevector sum of the separate components of deflection angle enumeratedabove, and will therefore be proportional to the required deflectionangle.

In a preferred form in. accordance with the invention the gyroscoperoto' is mounted on, and driven through a Hookes J'oint from an electricmotor. A spindle is attached to the rotor and carries a dome of highelectrical conductivity having the form of a spherical cap concentricwith the kinematic centre of the liookes joint. The centre of gravit ofthe moving system comprising said gyroscope rotor and its coupling withthe optical system is at the :inematic centre of the Hookes joint. Thegyroscope is constrained through the medium of a magnetic system whichlinks the high conductivity dome and reacts on said dome through themedium of induced eddy currents when the rotor spins. The magnitude anddirection of said eddy current reaction may be controlled b known means,either through the medium of adjustable magnetic shunts associated withthe magnetic system, or through the control of electric currents inwindings which may link the magnetic system. Said magnetic system may beenergised either solely by electromagnetic means or jointly b acombination of electromagnetic windings and permanent magnets. In orderto ensure dynamic stability of the moving system, the moment of inertiaof the gyro rotor about its spin axis must exceed a certain limitingvalue which is defined jointly by the transverse inertia of said movingsystem and b the design of the magnet system. This condition isfulfilled by the use of a Hookes joint gyro mounting which enables theamount of non-spinning mass embodied in the moving system to be reducedto the lowest practicable limit.

Various features of the invention will now be described with referenceto the accompanying illustrations in which:

Fig. 1 is a perspective View, partly broken away showing one form ofsight in accordance with the invention,

Fig. 2 is a side sectional elevation of an alternative form of sight,

Fig. 3 is an enlarged sectional elevation of the gyroscope unit embodiedin the sight shown in Fig. 2,

Fig. 4 is a front view of the gyroscope rotor shown in Fig. 3 with themirror removed,

Fig. 5 is 'a' rear view'of the gyroscope rotor unit shown in Fig. 3,

Fig. 6' is a section elevation of an alternative magnetsystem to thatshown in Fig. 3,

Figs. 7 and 8 are detail views of the graticulle patterns embodied inthe sight shown in Fig. 2,

Fig. 9 is an electric circuit diagram of an installation of the sightshown in Fig. 2.

Referring to Fig. 1, an electric motor Iii drives a hollow shaft llconnected at one end through a spring coupling [2 to a second shaft !3which is located within and co-axial with the hollow shaft H. The end ofthe shaft l3 remote from the spring coupling 12 is connected through aHookes joint M to a spindle l5 terminating at its free end in a ball I6,and carrying between its ends a gyroscope rotor H and a dome is of highelectrical conductivity, preferably copper, in the form of a sphericalcap concentric with the kinematic centre of the I-lookes joint i4.

Surrounding the gyroscope and motor is a housing is in which is mounteda magnet system having four independent flux paths formed by the polepieces 2! and 22 and the intervening air gaps through which the copperdome passes. The magnet system is excited jointl by the radiallymagnetised annular permanent magnet 29, the electromagnetic windings 23which links all the flux paths, and the electromagnetic windings 24which link the flux paths individually. The ball l6 engages in a sleeve25 carried by an arm 21' forming one member of a, linkage indicatedgenerall at 28. An extension of a second member 29 of this linkagecarries a graticule 30 which is interposed in the optical system of thetelescopic sight formed by the eye lens 3!, the field lens 32, theobject lens 33 and the prisms 34 and 35, through which the target isobserved. The graticule 36 is situated near the common focal plane ofthe object and eye lenses of the sight in order to ensure sharpness andfreedom from parallax in its image. In order to ensure that motions ofthe spindle i5 and the sighting line defined by the graticule 30 arealways in the same or nearly the same directions relative to thehousing, the linkage 28 is arranged to introduce a reversal of directioninto relative motions of the ball l6 and the graticule 39 parallel tothe refracting edge of the prism 3 but no such reversal into relativemotions parallel to the refracting edge of the prism 35.

The housing R9, the base of the linkage 28, and the body of thetelescopic sight are coupled rigidl together on a. common mounting plateTl! carried on a bracket 'H which is fixed to and turns with theassociated gun or guns.

In operation, when the motor i6 is running, eddy currents are set up inthe dome [8 as a result of the relative motion between the dome and themagnetic flux which links it, and a mechanical drag is therefore imposedon; the dome. In general, the distribution of dra throughout the dome issuch as to provide a pure couple about the spindle I5, against which themotor I0 works, and a force which, acting on the spindle 55, provides aprecessing torque which causes the gyroscope to move towards a uniqueposition in relation to the magnet system in which the drag reduces to a.pure couple only. The instantaneous rate of precession of the gyroscopeis proportional within very close limits to its angular displacementfrom the position in which the drag reduces to a pure couple only, andis also dependent on the magnetic field strength in the air gaps of themagnet system. When the housing and magnet system are turned in relationto space axes, the processing action described causes the spindle l5 tofollow the angular motion of the housing with a lag which is determinedjointly by the excitation of the magnet system and the characteristicsof the angular motion of the housing. This lag, which is transmitted tothe optical system via the linkage 28 and the graticule 3|] constitutesthe aiming allowance indicated by the sight, and its characteristics inrelation to the motion of the housing may be controlled within widelimits by variation of the electric currents supplied to the windings 23and 24. Additional control over the relationship between aimingallowance and housing motion is also [provided by an adjustable magneticshunt consisting of the soft iron disc 36 mounted on the screwed bush 3!so that its distance from the rear face of the magnet system may bevaried. This adjustment is used during manufacture only, to compensatefor variations arising from manufacturing tolerances; when correctlyset, the disc 36 is locked in position by means of the slots 38 in itsedges and a locking screw not shown.

The deflection of the spindle I in relation to the housing is limited bya ring 39 which makes contact with the outside of the sleeve 25 when themaximum limit of the deflection is reached. The teeth 26 on the outsideof the sleeve 25, and a set of similar teeth on the inside of the ring39 form a locking arrangement which prevents sudden rotation of thedirection of deflection through a right angle owing to the precessingeffect of the reaction between the sleeve 25 and the ring 36 when thelimit of free deflection has been reached. The ring 39 may be coupled toan iris diaphragm consisting of the leaves 49, and to an external membercontrolling the supply of current to the motor I0, thereby providingmeans for automatically centralising the spindle I5 and the graticule 30when the gyroscope is not running.

A reference pattern fixed in relation to the sight body may be providedby the graticule pattern I32 on the surface of the field lens 32.

In the form shown in Figs. 2 to 5, the gyroscope rotor consistin of thewheel I1, the wheel hub 4|, the spindle l5, and the aluminum dome I8 isbelt driven from a motor (not shown in Figs. 2-5 but indicated at In inFig. 9), the belt en- 7 gaging with a hollow pulley 42 carried in theball race 43 in the flanged ball race housing 44. The spindle I5 passesthrough the opening in the pulley 42. The drive is transmitted from thepulley 42 to the wheel I! via a Hookes joint consisting of the pivotedspider 45 which engages with pivot cups 46 carried in the wheel hub 4|,and pivot cups 4! carried in lugs 48 projecting from the pulley 42, seeFig. 4. The spider 45 carries a light spring wire 49 which, by bearingagainst the hub 4| to varying extents when the Hookes joint is bentpartly corrects the performance of the gyroscope for secondary errorscaused by the inertia of the pulley 42 and the spider 45.

The dome l8 passes through gaps between four pairs of pole pieces 2I'and22 associated with a magnet system consisting of the body 50 and cover5|, together with the magnetising windings 23 and 24. The entiremagnetic system may conveniently be made from low hysteresis magneticalloy such as radiometal, but no permanent magnets are used in thisarrangement. The flange of the ball race housing 44 is spigoted into arecess in the outer face of the magnet means ofthe magnetic adjustingscrews 53 and for accidental variations in dimensions and magneticproperties of the components of the magnet.

system. In an alternative form of magnet system shown in Fig. 6, theouter pole pieces 24 are screwed directly into the magnet body 56, beingdirected radially towards the dome I8. With this arrangement magneticadjustments required during assembly are made by screwing the polesbodily towards or away from the dome and locking them in the correctposition by means of the lock nuts 55. r

The front face of the wheel I? carries a mirror 56 which forms part of areflector optical system shown in Fig. 2, all the mirrors being frontsilvered to prevent the formation of double images. In this system, thegraticule assembly 51, 58, illuminated by the lamp 59 acts as a sourceof light which is seen superposed on a direct view of the target by theobservers eye 66 via the gyro mirror 56, the mirror 6!, collimating lens62 and transmitting reflector 63, items BI,

62 and 63 being rigidly fixed to the body of the sight.

The gyroscope wheel I! has a ring of overhanging tabs 64 (shown in planview in Fig. 5) which project from its back face. By bending these tabstowards or away from the wheel as required during manufacture, thegyroscope rotor assembly can be so balanced that the image found by themirror 56 remains steady in spite of the rotor spin. The holes 65 in thetabs are. provided for the insertion of a bending tool .to.

facilitate this operation.

The action of the gyroscope magnet system in relation to angularmovement of the sight body is identical in this arrangement with thatdescribed for the sight shown in Fig. l. Angular deflections of thegyroscope rotor assembly from its normal position of symmetry inrelation'to the magnet system cause the direction in which the image ofthe illuminated graticule assembly 51, 58 is seen by the observer tochange in relation to the sight body, these changes in directionconstituting the indicated aiming allowances. The sight body I 33'iscarried on a bracket I 34 which upstands from and turns with the ring ofsix equally spaced apertures at the points where the straight lines ofthe pattern 51, and the curves of the pattern 58 cross. By constructingthe pattern of the graticule 5? in the form of radial lines, and that ofthe graticule 58 in the form of logarithmic spirals, the arrangement maybe made to constitute a simple rangefinder. As indicated in Fig. 2, theholder 66 carrying the graticule 5'1 may be coupled by gearin to theexternal control handle Bl moving over the scale 68 calibrated in targetspan, and;

the holder 69 carrying the graticule 58 may be coupled also by gearingto an external pulley (not shown). By setting the handle EI-to indicatetarget span, and turning the pulley coupled .to the holder 69 until thering of dots seen through the optical system just embraces the target.the position of thispulley; can

be made to indicate target range. In practice the range indicatingpulley may be coupled to remote operating mechanism (e. g. pedals), thecoupling also engaging with variable resistances which control theelectric currents supplied to the magnet windings. In order to avoidparallax efiects in the graticule image, the graticules i and 58 aremounted in the closest possible proximity with the transparent patternson the adjacent faces.

A reference graticule pattern whose image remains fixed in relation tothe sight body may also be provided if required. When fitted, thisgraticule may be illuminated by a separate lamp (not shown) which can becontrolled independently of the lamp 553 by means of an externalswitching system.

An arrangement by which the electric currents required to ensure correctoperation of the sight shown in Fig. 2 may be generated and supplied tothe sight is illustrated by Fig. 9 which shows a circuit diagram of theinstallation.

Referring to Fig. 9 the switches S1, S2, S3, S4, the fixed resistanceR24 and variable resistance R25 form the essential elements of theselector and dimmer control. The variable resistances R3 and R1 arecontrolled by range setting. The variable resistances R23, R5, R8 and R9are controlled by height setting. The height control also contains thefixed resistance R10. The variable resistances R11 and R12 arecontrolled by airspeed setting. The variable resistances R15, R16, R11and the reversing switches S5 and So are controlled by gun azimuthangle. The azimuth control also contains the fixed resistances R13, R14,and R18. The variable resistances R20, R21, R22 and the reversing switchS7 are controlled by gun elevation angle. The elevation control alsocontains the fixed resistance R19. The fixed resistances R1, R2, R4 andR6 are housed in the junction box.

Alternative arrangements to that shown in Fig. 9 may be used with thesight according to the conditions of operation and the performanceaccuracy required. Thus, if the sight is used with guns which fire onlystraight ahead as in fixed gun fighter aircraft and only moderateaccuracy is required, the ballistic computin system may be designed totake account only of range or of range and height, whilst if thegreatest possible accuracy is required in turret gun installationsconsiderably more complex computing circuits than that shown in Fig. 9may be employed, and additional independent variables such as ambienttemperature, and aircraft pitch, yaw and bank angles may be fed into thesystem.

We claim:

1. In a predictor gunsight, adjustable means for defining a sightingline, a gyroscope having a spindle, means operatively connecting saidspindle to said adjustable means for actuating the same, an electricallyconducting member mounted on the spindle to spin with the gyroscope andoffset along the spin axis of the same, a symmetrical group or magneticpole pieces arranged in .pairs at either side of said electricallyconductin member to impose an eddy current drag on said conductingmember and thereby on the rotation of the gyroscope, coils associatedwith at le'ast one pair of said magneticpole pieces, whereby the polestrengths of saidpole pieces may be modified, gun means with which saidgroup'of pole; pieces is fast whereby when the gyroscope is spinning andthe gun means is moved the eddy current drag r ed in said housingthrough the intermediary of a Hookes joint, means operatively connectingsaid gyroscope to said adjustable means to actuate the same, anelectrically conducting member operatively connected to said gyroscopeto spin with the same and ofiset along the spin axis of the gyroscope,and a symmetrical group of separate magnetic pole pieces arranged in aplurality of pairs at either side of said electrically conducting memberand all fixedly mounted in said housing whereby said electricallyconducting member is continuously subjected to eddy current drag, saidelectrically conducting member and group of pole pieces having theiraxes normally aligned, so that when the gun is moved to disalign theaxes of the electrically conducting member and the group of magneticpole pieces, a couple is set up about an axis perpendicular to said spinaxis whereby said gyroscope is precessed to follow the movement of thehousing and associated gun means with a lag dependent on the angularvelocity of the movement of the gun means and which represents therequired deflection angle.

'3. In a predictor gunsight, a telescope, a graticule interposed in theoptical field of the telescope, means mounting said graticule to moveacross said field to adjustably define a sighting line, a gyroscopehaving a spindle operatively connected with said graticule to locate thesame in accordance with the orientation of the gyroscope spin axis, anelectrically conducting member operatively connected to said spindle tospin with the gyroscope and offset along the axis of the same, gunmeans,.and a magnetic member mounted to move with said gun meanscomprising a plurality of individual pole pieces symmetrically arrangedabout a common axis in pairs at either side of said electricallyconducting member and normally aligned axially with said electricallyconducting member whereby said electrically conducting member iscontinuously subject to eddy current drag and said gyroscope spindle issubject to a couple about an axis perpendicular to the gyroscope spinaxis when the axes of the electrically conducting member and magneticmember become disaligned and said graticule is caused to move with saidgyroscope spin axis to follow angular movement of the gun means with alag which varies with the angular velocity of said movement.

4. In a predictor gunsight, a transparent mirror through which arelatively moving target may be viewed, an optical projection systemincluding a graticule operatively related to said mirror so 1 that animage of the graticule is projected on said mirror and appears to besuperposed on the target,-a gyroscope, an electrically conducting memberoperatively connecte'd'to said gyroscope to spin with the same-andoffset along the axis of the gyroscope,-gun imeans, a magnetic membermounted to move with said gun means and nor- 'mally aligned axially withsaid electrically conducting member whereby said electrically conductingmember is continuously subject to eddy current drag and to a couple atright angles to the spin axis when the axes of the electricallyconducting and magnetic members become disaligned, whereby on angularmovement of said gun means the gyroscope is processed to follow saidmovement with a lag which varies with the angular velocity of movementof said gun means, and a mirror associated with the gyroscope to spintherewith and to move with its spin axis, said mirror forming a part ofsaid optical projection system.

5. In a predictor gunsight, an optical system for defining a sightingline, gun means, means mounting said system to move as a whole with saidgun means said system having an adjustable element, a gyroscope mountedto have three degrees of freedom with respect to the gun means andoptical system, a connection between said gyroscope and the adjustableelement in the optical system, whereby the sighting line is defined inaccordance with the orientation of the gyroscope spin axis, and meansfor constraining the gyroscope to follow angular movement of the gunmeans with a lag depending on the angular speed of such movement, saidlast-named means comprising a part-spherical electrically conductingmember mounted to rotate symmetrically with the gyroscope spin axis andoperatively connected to said gyroscope and a circular group ofcircumferentially spaced, continuously magnetised pole piecessymmetrically arranged in a plurality of pairs on either side of saidpartspherical member and operatively connected to said gun means mountedto move as a whole therewith whereby, when the gyroscope is rotating,eddy currents are set up in the part-spherical member giving acontinuous drag on the spinning of'the gyroscope and setting up aprecessing couple about an axis perpendicular to the gyroscope spin axiswhen said spin axis does not coincide with the axis of the group ofmagnetic pole pieces. I

6. A predictor gunsight comprising a movable support adapted to movewith the gun, means for defining a sighting line carried by saidsupport, a gyroscope, means operatively connecting said gyroscope tosaid sighting means to move the latter and control the direction of thesighting line with respect to the spin axis of said gyroscope, and meanswhereby said gyroscope is actuated to constrain its spin axis to followangular movement of said support with a lag which indicates the requireddeflection angle, said last named means including an electricallyconducting member offset along the spinning axis of the gyroscope andoperatively connected with the gyroscope to spin therewith and amagnetic system movable with said support having a plurality of polepieces located on opposite sides of said electrically conducting memberand providing a plurality of independent flux paths therebetween, thepole pieces of said magnetic system being symmetrically arranged aboutan axis normally aligned with the axis of said electrically conductingmember, said member and pole pieces cooperating to set up an eddycurrent drag in said member which exerts a precessing couple about anaxis perpendicular to the gyroscope spin axis when the axes of saidmember and pole pieces become disaligned.

7. A predictor gunsight, according to claim 6 including individualelectromagnetic windings for said pole pieces and means for variablyexciting said windings.

8. A predictor gunsight according to claim 6 wherein the electricallyconducting member consists of a relatively thin dome-shaped element ofhigh electrical conductivity adapted to spin in the space between theopposed pole pieces of said magnetic system. 7

LESLIE BENNET CRAIGIE CUNNINGHAM.

HOWARD FORD.

JEFFERY WALTON BARNES.

B. SYKES.

MAURICE HANCOCK.

BERNARD WHEELER ROBINSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

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